Method and device for ultrasonic vibration

ABSTRACT

An ultrasonic vibration method and an ultrasonic vibration apparatus which do not have a directional property in the direction of vibrations are disclosed. A pair of ultrasonic horns ( 11 ), ( 12 ) each having an ultrasonic vibrator ( 13 ), ( 14 ) provided at an end portion thereof are disposed in an intersecting relationship to each other, and composite vibrations of transverse vibrations produced by the pair of ultrasonic horns ( 11 ), ( 12 ) when the other ultrasonic horns ( 12 ), ( 11 ) are excited to generate longitudinal vibrations are extracted at the intersecting point of the pair of horns ( 11 ), ( 12 ) and applied to a contact object member through a presser ( 22 ).

TECHNICAL FIELD

[0001] This invention relates to an ultrasonic vibration method and anultrasonic vibration apparatus, and more particularly to an ultrasonicvibration method and an ultrasonic vibration apparatus wherein a pair ofultrasonic horns coupled in an intersecting relationship to each otherare used.

BACKGROUND ART

[0002] A bonding apparatus and a bonding method for an electronic partwith bumps which utilizes ultrasonic vibrations are disclosed, forexample, in Japanese Patent Laid-Open No. Hei 11-45912. Here, a pair ofhorns are disposed in an opposing relationship to each other on a commonaxis, and a piezoelectric element is attached to each of the horns.Further, an attracting tool is provided at the center of a narrowconnecting portion intermediate between the opposing horns, and asemiconductor chip having bumps thereon is held by the attracting tool.Besides, the semiconductor chip here is resiliently held by and betweena spring and a rib from a direction substantially perpendicular to thedirection of the axis of the horns.

[0003] In the bonding apparatus and the bonding method described above,the semiconductor chip is subject to vibrations in the axial directionof the horns by the horns. In an initial stage, when the semiconductorchip is moved in the vibration direction with respect to a board, oxidefilms of the bumps and electrodes are broken. Then, as the bondingproceeds, the semiconductor chip slips with respect to the holding meansformed from the spring and the rib as a result of increase of thebonding force between the bumps and the electrodes thereby to connectthe bumps of the semiconductor chip and the electrodes of the board toeach other.

[0004] Such an ultrasonic bonding apparatus as disclosed Japanese PatentLaid-Open No. Hei 11-45912 has a problem in that, where it is used forbonding of a semiconductor chip, it sometimes fails to bond asemiconductor device of a type wherein a plurality of bumps are arrangedin arbitrary arrangement in such conditions that the bonding force ofall of the bumps is higher than a desired value and that no significantmechanical defect occurs. The ultrasonic bonding apparatus has a problemthat, for example, if ultrasonic vibrations are applied to asemiconductor chip wherein bumps are arranged along a periphery of anelectrode face of a semiconductor bare chip such that the vibrationdirection thereof is the same direction as that of one side of therectangular bare chip, then if the bonding conditions are optimized sothat the bonding strength of all bumps may be higher than apredetermined value, then those bumps disposed along the sides extendingin the direction perpendicular to the application direction of theultrasonic vibrations, particularly those bumps which are at cornerportions of the rectangle of the bare chip, are likely to suffer fromcratering.

[0005] Further, the ultrasonic bonding apparatus has a problem that, ifthe bonding conditions are set conversely so that such cratering asmentioned above may not occur with any of the bumps, then the bondingstrength of those bumps which are disposed on the sides of thesemiconductor chip which extend in parallel to the application directionof the ultrasonic vibrations does not reach a sufficient value. Such aphenomenon as just described appears conspicuously particularly where aboard having a low hardness such as a glass epoxy type board is used asa mounting substrate.

[0006] The present invention has been made in view of such problems asdescribed above, and it is an object of the present invention to providean ultrasonic vibration method and an ultrasonic vibration apparatus bywhich, where the apparatus is used as a bonding apparatus for asemiconductor chip wherein a plurality of bumps are arranged inarbitrary arrangement, the bumps can be bonded while a sufficientbonding strength is assured without causing mechanical damage such ascratering to occur with all of pad electrodes to be electricallyconnected.

DISCLOSURE OF INVENTION

[0007] The present invention relates to an ultrasonic vibration methodcharacterized in that a pair of ultrasonic horns are coupled in anintersecting relationship to each other and a first one of theultrasonic horns is excited to longitudinally vibrate in a lengthwisedirection thereof to cause a second one of the ultrasonic horns togenerate transverse vibrations while the second ultrasonic horn isexcited to longitudinally vibrate in a lengthwise direction thereof tocause the first ultrasonic horn to generate transverse vibrations suchthat composite vibrations of the transverse vibrations of the pair ofultrasonic horns which are produced at the intersecting couplingposition of the pair of ultrasonic horns are used as an output.

[0008] Here, the pair of ultrasonic horns may intersect substantiallyperpendicularly with each other and produce the composite vibrationswithin a plane substantially in parallel to a plane which includes thepair of ultrasonic horns. A presser may be provided at the intersectingcoupling position of the pair of ultrasonic horns and projectssubstantially perpendicularly to a plane which includes the pair ofultrasonic horns, and the presser may be pressed against a contactobject member to transmit the composite vibrations to the contact objectmember. The contact object member may be bonded to another member by thecomposite vibrations.

[0009] A pair of ultrasonic vibrators for individually providingvibrations to the pair of ultrasonic horns may be provided, and a phaserelationship between ultrasonic signals to be applied to the pair ofultrasonic vibrators may be adjusted. Adjustment of the phase of one ofthe pair of ultrasonic vibrators may be performed to adjust the phaserelationship between the signals to the pair of ultrasonic vibrators.The amplitudes or the angular velocities of or the phase differencebetween the ultrasonic signals to be applied to the pair of ultrasonicvibrators may be adjusted to vary the locus of the composite vibrationsin a plane parallel to a plane which includes the pair of ultrasonichorns. The pair of ultrasonic horns may have a length substantiallyequal to the wavelength of ultrasonic waves which propagate in the pairof ultrasonic horns or substantially equal to an integral number oftimes the wavelength. Each of the pair of ultrasonic horns may be fixedat least at a position of a node. The pair of ultrasonic horns mayintersect with and be coupled to each other each at a substantiallymiddle portion in the lengthwise direction thereof such that theamplitude of the longitudinal vibrations is maximum at the intersectingcoupling position, and be each fixed by fixing means at a positionspaced by a half wavelength or a distance of the sum of a halfwavelength and an integral number of times one wavelength from theintersecting coupling position

[0010] The present invention according to a first principal aspectrelating to an ultrasonic vibration apparatus relates to an ultrasonicvibration apparatus characterized in that it comprises a pair ofultrasonic horns coupled in an intersecting relationship to each other,and a first one of the ultrasonic horns is excited to longitudinallyvibrate in a lengthwise direction thereof to cause a second one of theultrasonic horns to generate transverse vibrations while the secondultrasonic horn is excited to longitudinally vibrate in a lengthwisedirection thereof to cause the first ultrasonic horn to generatetransverse vibrations such that composite vibrations of the transversevibrations of the pair of ultrasonic horns which are produced at theintersecting coupling position of the pair of ultrasonic horns are usedas an output.

[0011] Here, the pair of ultrasonic horns may intersect substantiallyperpendicularly with each other and produce the composite vibrationswithin a plane substantially in parallel to a plane which includes thepair of ultrasonic horns. The ultrasonic vibration apparatus may furthercomprise a presser provided at the intersecting coupling position of thepair of ultrasonic horns and projects substantially perpendicularly to aplane which includes the pair of ultrasonic horns, and the presser maybe pressed against a contact object member to transmit the compositevibrations to the contact object member. The contact object member maybe bonded to another member by the composite vibrations.

[0012] The ultrasonic vibration apparatus may further comprise a pair ofultrasonic vibrators for individually providing vibrations to the pairof ultrasonic horns, and a phase relationship between ultrasonic signalsto be applied to the pair of ultrasonic vibrators may be adjusted.Adjustment of the phase of at least one of the pair of ultrasonicvibrators may be performed. The amplitudes or the angular velocities ofor the phase difference between the ultrasonic signals to be applied tothe pair of ultrasonic vibrators may be adjusted to vary the locus ofthe composite vibrations in a substantially same plane.

[0013] The pair of ultrasonic horns may have a length substantiallyequal to the wavelength of ultrasonic waves which propagate in the pairof ultrasonic horns or substantially equal to an integral number oftimes the wavelength. Each of the pair of ultrasonic horns may be fixedat least at a position of a node by fixing means. The pair of ultrasonichorns may intersect with and be coupled to each other each at asubstantially middle portion in the lengthwise direction thereof suchthat the longitudinal vibrations exhibits a maximum amplitude at theintersecting coupling position, and be each fixed by fixing means at aposition spaced substantially by a half wavelength or a distance of thesum of a half wavelength and an integral number of times one wavelengthfrom the intersecting coupling position. An odd-numbered order naturalfrequency of the transverse vibrations of the first ultrasonic horn maysubstantially coincide with the frequency of an ultrasonic vibrator ofthe second ultrasonic horn which intersects with the first ultrasonichorn such that the transverse vibrations thereof substantially resonatewith the ultrasonic vibrations of the second ultrasonic horn.

[0014] The present invention according to another principal aspectrelating to an ultrasonic vibration apparatus relates to an ultrasonicvibration apparatus characterized in that it comprises a pair ofultrasonic horns coupled in a substantially intersecting relationship toeach other in a predetermined plane, an ultrasonic vibrator attached toan end portion of each of the ultrasonic horns, an ultrasonic oscillatorfor supplying ultrasonic signals to the pair of ultrasonic vibrators,and a presser provided at the intersecting coupling position of the pairof ultrasonic horns for being pressed against a contact object member,and that the pair of ultrasonic horns are excited to individuallyvibrate longitudinally such that the contact object member is bondedthrough the presser by composite vibrations of transverse vibrationsproduced at the intersecting coupling position.

[0015] Here, the ultrasonic vibration apparatus may further comprisephase adjustment means for adjusting the phase of the ultrasonic signalsto be applied to the pair of ultrasonic vibrators. The phase adjustmentmeans may be provided between at least one of the ultrasonic vibratorsand the ultrasonic oscillator. The amplitudes or the angular velocitiesof or the phase difference between the ultrasonic signals to be appliedto the pair of ultrasonic vibrators may be adjusted to vary the locus ofthe composite vibrations in the predetermined plane.

[0016] One of the ultrasonic horns may have a length substantially equalto the wavelength of ultrasonic waves which propagate in the ultrasonichorns or substantially equal to an integral number of times thewavelength. Each of the pair of ultrasonic horns may be fixed at leastat a position of a node by fixing means. The pair of ultrasonic hornsintersect with and may be coupled to each other each at a substantiallymiddle portion in the lengthwise direction thereof such that theamplitude of the longitudinal vibrations is maximum at the intersectingcoupling position, and be each fixed by fixing means at a positionspaced by a half wavelength or a distance of the sum of a halfwavelength and an integral number of times one wavelength from theintersecting coupling position. An odd-numbered order natural frequencyof the transverse vibrations of a first one of the ultrasonic horns maysubstantially coincide with the frequency of the ultrasonic vibrator ofa second one of the ultrasonic horns which intersects with the firstultrasonic horn such that the transverse vibrations thereofsubstantially resonate with the ultrasonic vibrations of the secondultrasonic horn.

[0017] A preferred form of the invention included in the presentinvention relates to an ultrasonic vibration method and an ultrasonicvibration apparatus for bonding a semiconductor chip which forms a flipchip IC to an electronic circuit board using ultrasonic waves,configured such that it comprises a pair of ultrasonic oscillators, aphase adjustment apparatus for adjusting the phase difference betweenultrasonic signals outputted from the ultrasonic oscillators, twoultrasonic vibrators for generating ultrasonic waves in response to theultrasonic signals from the ultrasonic oscillator, and a pair ofultrasonic horns intersecting in a substantially cross-shape with eachother on an X-Y plane, and the ultrasonic vibrations are attachedindividually to the ultrasonic horns and the amplitude and the angularvelocity of the vibrations in the X-axis direction, the amplitude andthe angular velocity of the vibrations in the Y-axis direction and thephase difference between the vibrations in the X-axis direction and theY-axis direction are individually adjusted to appropriate values suchthat the semiconductor chip is pressed in vibrations against theelectronic circuit board with an optimum locus in the X-Y plane toimprove the bonding strength and the uniformity in bonding between thesemiconductor chip and the electronic circuit board.

[0018] Here, the ultrasonic horns for the X-axis direction and theY-axis direction which are coupled in an intersecting relationship in asubstantially cross-shape to each other may have a length substantiallyequal to an integral number of times the wavelength of ultrasonic waveswhich propagate in the ultrasonic horns, and besides may each be fixedat a position spaced by a ½ wavelength or a distance of the sum of a ½wavelength and a distance of an integral number of times one wavelengthfrom the center of the ultrasonic horns. Further, the pair of ultrasonichorns disposed in an intersecting relationship with each other generatesuch vibrations that longitudinal vibrations in one of the X-axisdirection and the Y-axis direction by ultrasonic waves cause theultrasonic horn for the other of the X-axis direction and the Y-axisdirection to generate transverse vibrations and composite vibrationsproduced by synthesis of the transverse vibrations of the ultrasonichorn for the X-axis direction and the transverse vibrations of theultrasonic horn for the Y-axis direction form an arbitrary locus in theX-Y plane. Further, where an odd-numbered order natural frequency of thetransverse frequency of the ultrasonic horn in this instance is setcoincident with the frequency of the ultrasonic oscillator, thetransverse vibrations resonate with the ultrasonic vibrations.Consequently, an ultrasonic vibration apparatus which generatespreferred vibrations is obtained.

[0019] Where such an ultrasonic vibration method and an ultrasonicvibration apparatus as described above are used for bonding of asemiconductor chip formed from a flip chip IC and an electronic circuitboard, even if the arrangement of bumps of the semiconductor chipdiffers in various manners, since the direction of the ultrasonicvibrations includes components of the two directions of the X-axisdirection and the Y-axis direction, a bonding quality having a stablebonding strength and a uniformity in bonding is achieved without beinginfluenced by the arrangement direction of bumps.

BRIEF DESCRIPTION OF DRAWINGS

[0020]FIG. 1 is a perspective view of essential part of an ultrasonicvibration apparatus to which an ultrasonic vibration method of anembodiment is applied;

[0021]FIG. 2 is a front elevational view of essential part of theultrasonic vibration apparatus;

[0022]FIG. 3 is a sectional view taken along line A-A of FIG. 2;

[0023]FIG. 4 is a plan view similar to FIG. 3 but illustratingtransverse vibrations generated by a pair of horns extendingperpendicularly to each other;

[0024] FIGS. 5(A) to 5(I) are plan views showing a locus of thevibrations;

[0025]FIG. 6 is a front elevational view showing a semiconductor chip ina bonded state;

[0026]FIG. 7 is a bottom plan view of the semiconductor chip held by apresser;

[0027]FIG. 8 is a vertical sectional view of the semiconductor devicebonded;

[0028]FIG. 9 is a plan view of essential part of an ultrasonic vibrationapparatus of another embodiment; and

[0029]FIG. 10 is a plan view of essential part of an ultrasonicvibration apparatus of a further embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] FIGS. 1 to 3 show a general configuration of an ultrasonicvibration apparatus to which an ultrasonic vibration method according toan embodiment of the present invention is applied. The presentultrasonic vibration apparatus includes a pair of ultrasonic horns 11and 12 disposed perpendicularly to each other as shown in FIG. 1. Here,the ultrasonic horn 11 is disposed in the direction of an X-axis whilethe ultrasonic horn 12 is disposed in the direction of a Y-axis.Ultrasonic vibrators 13 and 14 are attached to end portions of the pairof ultrasonic horns 11 and 12, respectively. The ultrasonic vibrators 13and 14 cause the ultrasonic horns 11 and 12 to generate vibrations inthe lengthwise directions, that is, in the longitudinal directions,respectively.

[0031] The ultrasonic horn 11 is connected at an intermediate positionbetween the center and each of the opposite ends thereof, that is, ateach nodal point to fixed rods 16 through arms 15 on the opposite sidesthereof. Similarly, the ultrasonic horn 12 for the Y-axis direction iscoupled at an intermediate position between a middle portion and each ofthe opposite ends in the longitudinal direction thereof to fixed rods 18through arms 17 on the opposite side thereof. The fixed rods 16 and 18are securely mounted on a lower face of a support plate 19 shown in FIG.2. The support plate 19 is securely mounted at an end portion of avertical shaft 20 which is movable upwardly and downwardly in thedirection of a Z-axis A presser 22 is mounted on a lower face at anintersecting position of the pair of ultrasonic horns 11 and 12.

[0032] In order to cause the ultrasonic horns 11 and 12 to vibratelongitudinally, a control circuit 25 shown in FIG. 3 is provided. Thecontrol circuit 25 is connected to a pair of ultrasonic oscillators 27and 28. Here, a phase adjuster 29 is connected between the ultrasonicoscillator 28 for the Y-axis direction and the control circuit 25 sothat a predetermined phase difference may be produced between outputs ofthe pair of ultrasonic oscillators 27 and 28.

[0033] In such a configuration as described above, the ultrasonicoscillators 27 and 28 supply ultrasonic signals to the ultrasonicvibrators 13 and 14, respectively, under the control of the controlcircuit 25. The phase difference between the pair of ultrasonicoscillators 27 and 28 in this instance is adjusted arbitrarily by meansof the phase adjuster 29.

[0034] The ultrasonic horn 11 for the X-axis direction generateslongitudinal vibrations in the longitudinal direction thereof as seen inFIG. 3 in response to the ultrasonic signal applied to the ultrasonicoscillator 13. The longitudinal vibrations exhibit a maximum amplitudeat the opposite ends and the central portion of the ultrasonic horn 11and besides exhibit the amplitude of 0 at each of the positions at eachof which the ultrasonic horn 11 is fixed by a pair of fixed rods 16.From such longitudinal vibrations as just described, the ultrasonic horn12 for the Y-axis direction which extends perpendicularly to theultrasonic horn 11 for the X-axis direction produces transversevibrations.

[0035] Similarly, the ultrasonic oscillator 14 excites the ultrasonichorn 12 for the Y-axis direction to generate longitudinal vibrations inresponse to the ultrasonic signal applied from the ultrasonic oscillator28. Consequently, the ultrasonic horn 11 for the X-axis directiongenerates transverse vibrations. FIG. 4 illustrates the transversevibrations of the pair of ultrasonic horns 11 and 12. Compositevibrations of the transverse vibrations are extracted from theintersecting coupling position of the pair of ultrasonic horns 11 and12. In particular, the composite vibrations are extracted at the centralposition of the ultrasonic horns 11 and 12 at which the presser 22 isprovided. Such composite vibrations are composite vibrations with whichan end portion of the composite vibrations shown in FIG. 4 draws anarbitrary locus depending upon the amplitudes and angular velocities ofand the phase difference between the ultrasonic vibrations applied tothe ultrasonic horn 11 for the X-axis direction and the ultrasonic horn12 for the Y-axis direction.

[0036] In this manner, with the ultrasonic vibration method and theultrasonic vibration apparatus of the present embodiment, ultrasonicsignals outputted from the pair of ultrasonic oscillators 27 and 28 areapplied to the ultrasonic vibrators 13 and 14, respectively. At thistime, the phases of the two ultrasonic signals are adjusted by means ofthe phase adjuster 29. It is to be noted that the phase adjuster may beformed from a timer which displaces the starting time of oscillation.

[0037] The pair of ultrasonic horns 11 and 12 to which the ultrasonicvibrators 13 and 14 are attached, respectively, are disposed such thatthe directions of vibrations thereof may be perpendicular to each other.Now, it is assumed that the vibrations applied to the ultrasonic horn 11for the X-axis direction are x=Acosω₁t in the X-axis direction.Meanwhile, it is assumed that the vibrations in the Y-axis directionapplied by the ultrasonic oscillator 14 are y=Bcos(ω₂t−α). It is to benoted here that t represents time.

[0038] The amplitudes A and B of the two ultrasonic horns 11 and 12 canbe set freely by adjusting the intensity of the ultrasonic signals ofthe pair of ultrasonic oscillators 27 and 28 . Also the phase differenceα between the vibrations in the two directions can be adjustedarbitrarily by means of such a phase adjuster 29 as describedhereinabove.

[0039] The angular velocity ω₁ of the vibrations in the X-axis directionand the angular velocity ω₂ of the vibrations in the Y-axis directionare set coincident with the angular velocity W₁ corresponding to thenatural frequency in the longitudinal direction of the ultrasonic horn11 for the X-axis direction and the angular velocity ω₂ corresponding tothe natural frequency of the longitudinal vibrations in the Y-axisdirection, respectively. Consequently, the amplitude at the intersectingcoupling position of the pair of ultrasonic horns 11 and 12 becomes amaximum amplitude. In other words, the angular velocities ω₁ and ω₂ ofthe vibrations in the two directions are selected based on a design ofthe ultrasonic horns 11 and 12.

[0040] First, excitation with vibrations of x=Acosω₁t by the ultrasonicoscillator 13 for the X-axis direction is described. Referring to FIG.3, the length of the ultrasonic horn 11 for the X-axis direction isdesigned equal to the length of one wavelength of longitudinalvibrations of the ultrasonic horn 11 by ultrasonic vibrations. Further,the fixed rods 16 are fixed at the positions of 0.5 wavelengths. It isto be noted that the fixed rods 16 may be formed integrally with or asseparate members from the ultrasonic horn 11.

[0041] In FIG. 3, the amplitude of the longitudinal vibrations in theX-axis direction is represented by a displacement in the Y-axisdirection for the convenience of illustration. The amplitude of thelongitudinal vibrations of the ultrasonic horn 11 exhibits it maximumamplitude at the movable pressurization point of the ultrasonic horn 11at which the presser 22 is provided. Also the ultrasonic horn 12 for theY-axis direction is fixed by the fixed rods 18 similarly.

[0042] The third order natural frequency of vibrations in the X-axisdirection of the ultrasonic horn 12 for the Y-axis direction, that is,transverse vibrations is set so as to coincide with the naturalfrequency of ultrasonic vibrations in the X-axis direction. Accordingly,when the movable pressurization point tends to move in the X-axisdirection by a longitudinal vibration of the ultrasonic horn 11 for theX-axis direction, a third order transverse vibration of the ultrasonichorn 12 for the Y-axis direction is excited, and the ultrasonic horn 12for the Y-axis direction forms such an amplitude vibration as shown inFIG. 3. Accordingly, the intersecting position between the ultrasonichorn 11 for the X-axis direction and the ultrasonic horn 12 for theY-axis direction, that is, the movable pressurization point, moves witha substantially same vibration x=Acosω₁t in the X-axis direction asshown in FIG. 3.

[0043] Then, in such a state as described above, vibrations ofy=Bcos(ω₂t−α) are applied to the ultrasonic horn 12 for the Y-axisdirection by means of the ultrasonic oscillator 14. Here, since theangular velocity of the third order natural frequency in the transversedirection between the fixed rods 16 of the ultrasonic horn 11 for theX-axis direction is set so as to coincide with ω₂, the movablepressurization point moves with a substantially same vibrationy=Bcos(ω₂t−α) in the Y-axis direction similarly as described above.

[0044] Consequently, the intersecting position of the ultrasonic horns11 and 12 at which the presser 22 is provided, that is, the movablepressurization point, is transversely vibrated in both of the X-axisdirection and the Y-axis direction. Vibration states of the cross-shapedultrasonic horns in this state are shown in FIG. 4. In particular, FIG.4 shows only patterns of the transverse vibrations of the ultrasonichorns 11 and 12. Accordingly, if the amplitudes A and B of thevibrations then and the angular velocities ω₁ and ω₂ of and the phasedifference α between the vibrations are selected in such a manner asgiven in the following table, the locus by the vibrations of the movablepressurization point at which the presser 22 is provided becomes such asgiven below. The locus of the end of the vector of the compositevibrations then is represented by patterns of FIGS. 5(A) to 5(I). ω A Bα x y FIG. A 0 0 Acosωt 0 A 0 B 0 0 Bcosωt B A A 0 Acosωt Acosωt C whenω₁ = ω₂ = ω A A 90° Acosωt Asinωt D A A 180° Acosωt -Acosωt E A A 270°Acosωt -Asinωt F A 2A 90° Acosωt 2Asinωt G when ω₁ = ω, A A 90° AcosωdtAsin2ωdt H ω₂ = 2ω when ω₁ = ω, A A 90° Acosωt Asin(107 I ω₂ = ω = Δ ω +Δ ω) t

[0045] Now, use of such an ultrasonic vibration method as describedabove and the ultrasonic vibration apparatus which uses the method tobond a semiconductor bare chip 40 and a board 45 to each other isdescribed with reference to FIGS. 2 and 6 to 8. The semiconductor chip40 formed from a bare chip has pad electrodes 41 formed along peripheraledge portions on an electrode face thereof as shown in FIGS. 6 and 7. Itis to be noted that the face on which the pad electrodes 41 are formedis coated with a surface protecting layer formed from, for example, asilicon nitride layer or a polyimide layer and only portions thereof forthe pad electrodes 41 are open. Bumps 42 made of a conductor such as ametal are formed on such pad electrodes 41. Consequently, thesemiconductor chip 40 is formed as of the peripheral pad type.

[0046] On the other hand, the board 45 onto which the semiconductor chip40 is to be flip chip mounted is made of, for example, a ceramics typematerial, and electrodes formed from lands 46 made of a conductivematerial such as, for example, copper and coated with nickel, gold orthe like by surface plating processing are formed at positions of theboard 45 corresponding to the pad electrodes 41 of the semiconductorbare chip 40 to be mounted. The lands 46 are connected to wiring lineportions formed on the front surface or the rear surface of the board45.

[0047] In order to bond the semiconductor chip 40 to the board 45 havingsuch a configuration as described above, the board 45 is placed onto abase 47 as shown in FIGS. 2 and 6, and the semiconductor chip 40 isdisposed on the lower side of the presser 22 of the ultrasonic bondingapparatus such that the surface thereof on which the pad electrodes 41are provided is directed downwardly. Then, in this state, the ultrasonicvibrators 13 and 14 are driven by the ultrasonic oscillators 27 and 28to cause the ultrasonic horns 11 and 12 to individually vibratelongitudinally, respectively, such that composite vibrations aregenerated at the position at which the presser 22 is provided. By suchcomposite vibrations, frictional heat is generated between end portionsof the bumps 42 on the pad electrodes 41 and the lands 46 of the board45. Consequently, at least the end portions of the bumps 42 or the lands46 are melted and the pad electrodes 41 and the lands 46 are connectedto each other, whereby such a semiconductor device as shown in FIG. 8 isobtained.

[0048] The cross-shaped horns 11 and 12 are moved downwardly in a statewherein the movable pressurization point formed at the intersectingposition of the pair of ultrasonic horns 11 and 12 vibrates in variousloci as shown in Table 1 and in FIG. 5 by ultrasonic vibrations in thismanner, whereupon the presser 22 presses the semiconductor bare chip 40against the board 45. Since the contact face of the presser 22 with thesemiconductor chip 40 is designed so as to have high friction, thesemiconductor chip 40 is ultrasonic bonded to the electronic circuitboard 45 while drawing the same locus as that of the presser 22. Sincean arbitrary locus can be selected from among such various loci ofvibrations as shown by the patterns of FIGS. 5(A) to 5(I), if a uniformvibration pattern which does not rely upon the arrangement direction ofthe bumps 42 formed on the electrode face of the semiconductor bare chip40, then a stable bonding quality is obtained.

[0049] It is to be noted that, in such an ultrasonic vibration methodand an ultrasonic variation apparatus as described above, the form orlength of vibrations or the fixed position of each of the ultrasonichorn 11 for the X-axis direction and the ultrasonic horn 12 for theY-axis direction can be selected arbitrarily. For example, it ispossible to set the length of the ultrasonic horn 11 for the X-axisdirection equal to the length of one wavelength of longitudinalvibrations generated with the ultrasonic horn 11 and make the firstorder natural frequency of transverse vibrations generated with theultrasonic horn 12 for the Y-axis direction coincide with the frequencyof ultrasonic vibrations. Consequently, vibrations in the transversedirection of the ultrasonic horn 12 for the Y-axis direction become suchas illustrated in FIG. 9.

[0050] Alternatively, it is possible to set, as shown in FIG. 10, thelength of the ultrasonic horn 11 for the X-axis direction to the lengthof 2 wavelengths of longitudinal vibrations generated with theultrasonic horn 11 and make the third order natural frequency oftransverse vibrations of the ultrasonic horn 12 for the Y-axis directioncoincide with the frequency of the ultrasonic vibrations.

[0051] It is to be noted that, although the shapes and the fixedpositions of the ultrasonic horn 11 for the X-axis direction and theultrasonic horn 12 for the Y-axis direction shown in FIGS. 9 and 10 aredrawn symmetrically with each other, it is only necessary to design sothat longitudinal vibrations of the ultrasonic horn 11 for the X-axisdirection and the ultrasonic horn 12 for the Y-axis direction mayresonate with transverse vibrations of the ultrasonic horn 12 for theY-axis direction and the ultrasonic horn 11 for the X-axis direction,respectively, and the ultrasonic horns 11 and 12 may not necessarily beformed symmetrically.

[0052] According to a principal aspect of the present invention relatingto an ultrasonic vibration method, a pair of ultrasonic horns arecoupled in an intersecting relationship to each other and a first one ofthe ultrasonic horns is excited to longitudinally vibrate in alengthwise direction thereof so that transverse vibrations are generatedwith a second one of the ultrasonic horn while the second ultrasonichorn is excited to longitudinally vibrate in a longitudinal directionthereof so that transverse vibrations are generated with the firstultrasonic horn such that composite vibrations of the transversevibrations of the pair of ultrasonic horns produced at the intersectingcoupling point of the pair of ultrasonic horns are used as an output.

[0053] Accordingly, with such an ultrasonic vibration method as justdescribed, vibrations of various loci can be generated at theintersecting coupling position of the pair of ultrasonic horns in aplane parallel to the plane which includes the pair of ultrasonic horns.

[0054] According to a principal aspect of the present invention relatingto an ultrasonic vibration apparatus, it comprises a pair of ultrasonichorns coupled in a substantially intersecting relationship to each otherin a predetermined plane, an ultrasonic vibrator attached to an endportion of each of the ultrasonic horns, an ultrasonic oscillator forsupplying ultrasonic signals to the pair of ultrasonic vibrators, and apresser provided at the intersecting coupling position of the pair ofultrasonic horns for being pressed against a contact object member, andthe pair of ultrasonic horns are excited to individually vibratelongitudinally such that the contact object member is bonded through thepresser by composite vibrations of transverse vibrations produced at theintersecting coupling position.

[0055] Accordingly, with such an ultrasonic vibration apparatus as justdescribed, by pressing the presser provided at the intersecting couplingposition of the pair of ultrasonic horns against the contact objectmember, composite vibrations produced at the intersecting couplingposition of the pair of ultrasonic horns can be applied to the contactobject member, whereby the contact object member can be bonded toanother member while the contact object member is ultrasonic vibrated.Thus, an ultrasonic bonding apparatus which uses ultrasonic vibrationscomposed of composite vibrations described above is provided.

What is claimed is:
 1. An ultrasonic vibration method, characterized inthat a pair of ultrasonic horns are coupled in an intersectingrelationship to each other and a first one of said ultrasonic horns isexcited to longitudinally vibrate in a lengthwise direction thereof tocause a second one of said ultrasonic horns to generate transversevibrations while the second ultrasonic horn is excited to longitudinallyvibrate in a lengthwise direction thereof to cause the first ultrasonichorn to generate transverse vibrations such that composite vibrations ofthe transverse vibrations of said pair of ultrasonic horns which areproduced at the intersecting coupling position of said pair ofultrasonic horns are used as an output.
 2. An ultrasonic vibrationmethod according to claim 1, characterized in that said pair ofultrasonic horns intersect substantially perpendicularly with each otherand produce the composite vibrations within a plane substantially inparallel to a plane which includes said pair of ultrasonic horns.
 3. Anultrasonic vibration method according to claim 1, characterized in thata presser is provided at the intersecting coupling position of said pairof ultrasonic horns and projects substantially perpendicularly to aplane which includes said pair of ultrasonic horns, and said presser ispressed against a contact object member to transmit the compositevibrations to the contact object member.
 4. An ultrasonic vibrationmethod according to claim 3, characterized in that the contact objectmember is bonded to another member by the composite vibrations.
 5. Anultrasonic vibration method according to claim 1, characterized in thata pair of ultrasonic vibrators for individually providing vibrations tosaid pair of ultrasonic horns are provided, and a phase relationshipbetween ultrasonic signals to be applied to said pair of ultrasonicvibrators is adjusted.
 6. An ultrasonic vibration method according toclaim 5, characterized in that adjustment of the phase of one of saidpair of ultrasonic vibrators is performed to adjust the phaserelationship between the signals to said pair of ultrasonic vibrators.7. An ultrasonic vibration method according to claim 5, characterized inthat the amplitudes or the angular velocities of or the phase differencebetween the ultrasonic signals to be applied to said pair of ultrasonicvibrators is adjusted to vary the locus of the composite vibrations in aplane parallel to a plane which includes said pair of ultrasonic horns.8. An ultrasonic vibration method according to claim 1, characterized inthat said pair of ultrasonic horns have a length substantially equal tothe wavelength of ultrasonic waves which propagate in said pair ofultrasonic horns or substantially equal to an integral number of timesthe wavelength.
 9. An ultrasonic vibration method according to claim 1,characterized in that each of said pair of ultrasonic horns is fixed atleast at a position of a node.
 10. An ultrasonic vibration methodaccording to claim 8, characterized in that said pair of ultrasonichorns intersect with and are coupled to each other each at asubstantially middle portion in the lengthwise direction thereof suchthat the amplitude of the longitudinal vibrations is maximum at theintersecting coupling position, and are each fixed by fixing means at aposition spaced by a half wavelength or a distance of the sum of a halfwavelength and an integral number of times one wavelength from theintersecting coupling position.
 11. An ultrasonic vibration apparatus,characterized in that it comprises a pair of ultrasonic horns coupled inan intersecting relationship to each other, and a first one of saidultrasonic horns is excited to longitudinally vibrate in a lengthwisedirection thereof to cause a second one of said ultrasonic horns togenerate transverse vibrations while the second ultrasonic horn isexcited to longitudinally vibrate in a lengthwise direction thereof tocause the first ultrasonic horn to generate transverse vibrations suchthat composite vibrations of the transverse vibrations of said pair ofultrasonic horns which are produced at the intersecting couplingposition of said pair of ultrasonic horns are used as an output.
 12. Anultrasonic vibration apparatus according to claim 11, characterized inthat said pair of ultrasonic horns intersect substantiallyperpendicularly with each other and produce the composite vibrationswithin a plane substantially in parallel to a plane which includes saidpair of ultrasonic horns.
 13. An ultrasonic vibration apparatusaccording to claim 11, characterized in that it further comprises apresser provided at the intersecting coupling position of said pair ofultrasonic horns and projects substantially perpendicularly to a planewhich includes said pair of ultrasonic horns, and said presser ispressed against a contact object member to transmit the compositevibrations to the contact object member.
 14. An ultrasonic vibrationapparatus according to claim 13, characterized in that the contactobject member is bonded to another member by the composite vibrations.15. An ultrasonic vibration apparatus according to claim 11,characterized in that it further comprises a pair of ultrasonicvibrators for individually providing vibrations to said pair ofultrasonic horns, and a phase relationship between ultrasonic signals tobe applied to said pair of ultrasonic vibrators is adjusted.
 16. Anultrasonic vibration apparatus according to claim 15, characterized inthat adjustment of the phase of at least one of said pair of ultrasonicvibrators is performed.
 17. An ultrasonic vibration apparatus accordingto claim 11, characterized in that the amplitudes or the angularvelocities of or the phase difference between the ultrasonic signals tobe applied to said pair of ultrasonic vibrators is adjusted to vary thelocus of the composite vibrations in a substantially same plane.
 18. Anultrasonic vibration apparatus according to claim 11, characterized inthat said pair of ultrasonic horns have a length substantially equal tothe wavelength of ultrasonic waves which propagate in said pair ofultrasonic horns or substantially equal to an integral number of timesthe wavelength.
 19. An ultrasonic vibration apparatus according to claim11, characterized in that each of said pair of ultrasonic horns is fixedat least at a position of a node by fixing means.
 20. An ultrasonicvibration apparatus according to claim 11, characterized in that saidpair of ultrasonic horns intersect with and are coupled to each othereach at a substantially middle portion in the lengthwise directionthereof such that the longitudinal vibrations exhibits a maximumamplitude at the intersecting coupling position, and are each fixed byfixing means at a position spaced substantially by a half wavelength ora distance of the sum of a half wavelength and an integral number oftimes one wavelength from the intersecting coupling position.
 21. Anultrasonic vibration apparatus according to claim 11, characterized inthat an odd-numbered order natural frequency of the transversevibrations of the first ultrasonic horn substantially coincides with thefrequency of an ultrasonic vibrator of the second ultrasonic horn whichintersects with the first ultrasonic horn such that the transversevibrations thereof substantially resonate with the ultrasonic vibrationsof the second ultrasonic horn.
 22. An ultrasonic vibration apparatus,characterized in that it comprises a pair of ultrasonic horns coupled ina substantially intersecting relationship to each other in apredetermined plane, an ultrasonic vibrator attached to an end portionof each of said ultrasonic horns, an ultrasonic oscillator for supplyingultrasonic signals to the pair of ultrasonic vibrators, and a presserprovided at the intersecting coupling position of said pair ofultrasonic horns for being pressed against a contact object member, andthat said pair of ultrasonic horns are excited to individually vibratelongitudinally such that the contact object member is bonded throughsaid presser by composite vibrations of transverse vibrations producedat the intersecting coupling position.
 23. An ultrasonic vibrationapparatus according to claim 22, characterized in that it furthercomprises phase adjustment means for adjusting the phase of theultrasonic signals to be applied to said pair of ultrasonic vibrators.24. An ultrasonic vibration apparatus according to claim 23,characterized in that said phase adjustment means is provided between atleast one of said ultrasonic vibrators and said ultrasonic oscillator.25. An ultrasonic vibration apparatus according to claim 22,characterized in that the amplitudes or the angular velocities of or thephase difference between the ultrasonic signals to be applied to saidpair of ultrasonic vibrators is adjusted to vary the locus of thecomposite vibrations in the predetermined plane.
 26. An ultrasonicvibration apparatus according to claim 22, characterized in that one ofsaid ultrasonic horns has a length substantially equal to the wavelengthof ultrasonic waves which propagate in said ultrasonic horns orsubstantially equal to an integral number of times the wavelength. 27.An ultrasonic vibration apparatus according to claim 22, characterizedin that each of said pair of ultrasonic horns is fixed at least at aposition of a node by fixing means.
 28. An ultrasonic vibrationapparatus according to claim 22, characterized in that said pair ofultrasonic horns intersect with and are coupled to each other each at asubstantially middle portion in the lengthwise direction thereof suchthat the amplitude of the longitudinal vibrations is maximum at theintersecting coupling position, and are each fixed by fixing means at aposition spaced by a half wavelength or a distance of the sum of a halfwavelength and an integral number of times one wavelength from theintersecting coupling position.
 29. An ultrasonic vibration apparatusaccording to claim 22, characterized in that an odd-numbered ordernatural frequency of the transverse vibrations of a first one of saidultrasonic horns substantially coincides with the frequency of saidultrasonic vibrator of a second one of said ultrasonic horns whichintersects with the first ultrasonic horn such that the transversevibrations thereof substantially resonate with the ultrasonic vibrationsof the second ultrasonic horn.